2.2 Entropy Flashcards
Second law of thermodynamics is?
Entropy will always increase in a spontaneous process
Third law of thermodynamics is?
Entropy is temperature dependent
What is absolute zero temperature?
Theoretical point where there is no thermal motion (reactions stop)
0 kelvin = - 273.15°C
What is Entropy
The measure of disorder in the universe ~ sheldrake
What is the symbol for entropy?
S
What is entropy unit
J per mol per K
(NOT KJ LIKE IN ENTHALPY)
Entropy change of system=?
ΔS = S products - S reactants
Entropy change of surroundings=?
ΔS = Δq/T
q = heat change of surroundings
T = temperature
Total entropy change of universe=?
ΔS total = ΔS system + ΔS surroundings
For a reaction to occur spontaneously…
ΔS total, must be positive
As molecular movement / motion increases, entropy…
Increases
5 Entropy increase examples
- Temperature increasing
- Liquid boiling / increased moles of gas
- Ionic solids dissolving
- Number of molecules increasing
Δq =
ΔH recation = enthalpy change of the reaction
Products enthalpy - reactants enthalpy
NOTE: SWAP SIGN FOR SURROUNDINGS
Gibbs free energy?
Energy from a reaction free to do work
(allows to work if reaction is spontaneous or not)
Gibbs Equation
ΔG = ΔH - TΔS
When ΔG is less than 0
Exergonic
Reaction WILL be spontaneous
When ΔG is more than 0
Endergonic
Reactions needs energy input to be spontaneous
When ΔG = 0
System is in equilibrium
ΔG has to always be …………… to be spontaneous
Negative
Learn combinations of ΔH and ΔS when reaction is spontaneous
See table
Anabolic reactions (eg amino acids 》》peptides) have a …………. ΔG
Positive ( ∴ NOT spontaneous)
For all simple subunits forming complex molecules
Anabolic reactions use ……….. to allow reactions to be spontaneous
Coupling reactions
Pair with reactions such as hydrolysis of ATP to have an overall - ΔG
